Grinding wheel



FIG. 1 is a perspective view of the grinding wheel showing my new design;

FIG. 2 is an edge view of the grinding wheel, partially sectioned in the plane represented by lines 2--2 in FIG. 3;

FIG. 3 is a top plan view thereof; and

FIG. 4 is a bottom plan view thereof. 

The ornamental design for a grinding wheel, as shown and described. 